Merged thin film magnetic heads are used to perform both "write" and "read" operations on magnetic media. The write and read operations are performed by separate write and read thin film heads which are merged together in a single thin film structure. Typically, the write head is an inductive structure with a thin film core of ferromagnetic material having a gap with a multi-turn coil wrapped around the thin film core which generates magnetic fields across the gap in response to electrical signals in the coil. The read head is typically a magnetoresistive read sensor which detects magnetic field signals through the resistance changes of the element as a function of the strength of the magnetic flux being sensed by the read sensor.
The merged thin film magnetic head is typically employed to write (or record) data as magnetic signals on a recording surface of a recording media and to read the recorded data as magnetic signals. Examples of recording media include magnetic disks which rotate at high speed, or magnetic tape which is moved in a linear fashion. The merged thin film magnetic head is typically closely spaced from the recording surface, often on an air bearing slider which has an air bearing surface which rides on an air bearing at the surface of a rotating disk, but also as a contact or near contact transducer.
The writing of data is accomplished by a signal in the thin film coil which induces a magnetic flux in the core. The core has two opposed pole pieces which terminate in two pole tips separated by a thin gap. The magnetic flux induced by the coil creates a magnetic field which extends beyond the core at the gap and to the recording media, magnetizing the media. The reading of data is accomplished by a read sensor positioned adjacent to the gap and pole pieces and between two shields which "shield" the read sensor from the write flux.
So as to increase the density of data recorded on the recording media, it is desirable to reduce the physical size of the merged thin film magnetic head. But, reducing the size of the head reduces the room available for windings of the thin film coil. The top pole piece of the thin film merged head is formed on top of the thin film coil and is kept as flat as possible and as short as possible between the back gap and pole tip. The typical merged thin film magnetic head has only one layer for the thin film coil and, since the induced magnetic flux is directly related to the number of turns of the coil, has more than one turn of the coil spaced apart in the single layer in the yoke region between the pole tips and the back gap.
As the head is reduced in size, the distance between the pole tips and back gap must also be reduced. To attempt to maintain a plurality of turns for the thin film coil, it would be advantageous to stack the turns in layers. However, each added coil layer raises the coil by the thickness of the layer and of the associated insulation to a substantially greater height than the pole tips and back gap, so that the top pole piece becomes highly sloped (apex angle) towards the pole tip and is also sloped toward the back gap, resulting in a high profile head. As described in coassigned U.S. Pat. No. 5,621,596, Santini, the high apex angle and high sloping layers pose a problem in construction of the head. To reduce the slope angles, the region in the yoke for placement of the thin film coil must be placed a distance away from the pole tip and away from the back gap, lengthening the pole pieces and reducing their efficiency.